This invention is related to the field of nondestructive testing, and more particularly, to nondestructive testing utilizing ultrasonic waves.
A number of ultrasonic testing methods have been developed using ultrasonic waves. Bulk wave modes, for example, which propagate through a solid material, have been employed to detect flaws in parts and to measure the thicknesses of such parts. Although bulk ultrasonic waves may be utilized for the qualitative detection of flaws, bulk wave testing has not been sufficiently precise to quantify flaws as to their length, depth, orientation, etc. Bulk wave modes have also been suggested for use in determining the condition of the surface of a material. In this application, a test object is irradiated with ultrasound while immersed in water, the spectroscopy of the reflected ultrasonic waves providing an indication of peroidic or quasi-periodic roughness on the surface (see, e.g., F. Cohen-tenoudji et al., Caracterisation de surfaces rugueuses periodiques ou quasi-periodiques par spectroscopie ultrasonore, communication presentee a la huitieme conference mondiale sur less essais non destructifs, Cannes, Frances, Septembre, 1976; A. Jungman et al., Diffraction Experiments in Ultrasonic Spectroscopy; preliminary results on the characterization of periodic or quasi-periodic surfaces; Conference Proceedings, Ultrasonics International, pp. 385-396, Brighton, England 1977, published by IPC Business Press Limited).
The ultrasonic test methods which have been heretofore known and developed, however, are not sufficiently precise to accurately measure the dimensions of surface flaws, particularly the length of such flaws. The length of a flaw is a useful quantity to be determined, since it would be useful for considerable applications in materials testing where it can be related to the remaining useful life of a part containing the flaw. Thus, it would be advantageous to provide a nondestructive test which measures the length of a flaw and permits the flaw length to be monitored as the flaw dimensions change during the life of the part.